COMPUTER MODELING OF SUBSTRATE-BINDING TO LIPASES FROM RHIZOMUCOR-MIEHEI, HUMICOLA-LANUGINOSA, AND CANDIDA-RUGOSA

The substrate-binding sites of the triacyl glyceride lipases from Rhiz omucor miehei, Humicola lanuginosa, and Candida rugosa were studied by means of computer modeling methods. The space around the active site was mapped by different probes. These calculations suggested 2 separat e regions within the binding site. One region showed high affinity for aliphatic groups, whereas the other region was hydrophilic. The aliph atic site should be a binding cavity for fatty acid chains. Water mole cules are required for the hydrolysis of the acyl enzyme, but are prob ably not readily accessible in the hydrophobic interface, in which lip ases are acting. Therefore, the hydrophilic site should be important f or the hydrolytic activity of the enzyme. Lipases from R. miehei and H . lanuginosa are excellent catalysts for enantioselective resolutions of many secondary alcohols. We used molecular mechanics and dynamics c alculations of enzyme-substrate transition-state complexes, which prov ided information about molecular interactions important for the enanti oselectivities of these reactions.